Polycarboxylic acid copolymers having a polyalkylene glycol chain can have characteristics such as hydrophilicity, hydrophobicity, and steric repulsion as a result of adjusting their properties such as the chain length and the constitutional alkylene oxides. Thus, such copolymers are used in a wide variety of uses, including adhesives, sealants, dispersants, softening components, and detergent builders. Currently, the polycarboxylic acid copolymers are also expected to be used in admixtures for cement to be added to cement compositions, such as cement paste, mortar, and concrete.
Admixtures for cement have an ability to increase the fluidity of cement compositions so as to reduce the amount of water used in the cement compositions, thereby improving the properties such as strength and durability of the resulting hardened matter. Therefore, such admixtures are also called as water-reducing agents. Admixtures for cement which have an ability to disperse cement are also called as dispersants for cement. Admixtures for cement which contain a polycarboxylic acid polymer having a polyalkylene glycol chain among the admixtures (water-reducing agents) for cement exert a higher water-reducing ability than conventional naphthalene-type water-reducing agents, and thus achieve many good results as high-performance AE water-reducing agents. For example, dispersants and other additives for cement disclosed in Patent Literature 1 and Patent Literature 2 are very useful in the field of the art.
In recent years, researchers have proposed super-high-strength concrete having a low water-cement ratio. Such super-high-strength concrete is formed from cement containing silica fume. Such cement shows good workability even at a low water-cement ratio and excellently exerts strength in middle and long material age and strength of structures. For example, Patent Literature 3 proposes a polycarboxylic acid copolymer including structural units derived from a specific polyalkylene glycol ether monomer to be used with silica-fume-containing cement.